Will London's Rain Become a Pain for Athletes?

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Among the high-profile events at the Summer Olympics in London
are swimming, diving, and gymnastics -– all sports that happen
indoors, where wind speeds, temperature and humidity are
irrelevant.

As runners and cyclists increasingly hit the track and roads this
weekend, the weather will become a much bigger performance
factor. London is notoriously cool and wet, a pattern that was
even more extreme than usual in the weeks leading up to the
Games.

Humidity might be a concern for marathon runners and other
endurance athletes who need to sweat to cool off, said Matt
White, an environmental physiologist at Fraser University in
Burnaby, British Columbia. Rain can also make roads slick for
cyclists if it’s been dry for a while. And heavy downpours can
play with the minds of athletes who are used to training in dry
conditions.

“If I was talking to a coach about London, unless they had a heat
wave, I think the environment is not going to be a big
determinant,” Fraser said. “Rain is cooling, and if you’re
working hard, it can act like sweat evaporation.”

When it comes to weather, by far the biggest – and most
extensively studied – concern for athletes is a combination of
high heat and high humidity. The human body at work uses sweat to
dissipate the heat that builds with effort, but that sweat needs
to evaporate to have a cooling effect on core body temperature.

As air heats up, it can hold more and more moisture. And hot, wet
air severely compromises the ability of sweat to evaporate.

To prepare for the hot and humid conditions at the 2008 Summer
Games in Beijing, which ended up not being as extreme as
expected, many athletes went through heat-acclimation training
beforehand.

Fraser helped the U.S. men’s field hockey team prepare for the
Beijing Olympics by putting players in a room heated to 35
degrees Celsius (95 Fahrenheit) and 75 percent humidity. For an
hour a day for five days, the athletes worked out on a treadmill
or an exercise bike in the heated room – giving their bodies a
chance to adapt to exercising in hot and humid conditions.

With heat-acclimation regimens, an athlete’s body learns to sweat
sooner and to produce more diluted sweat, helping him or her
simultaneously stay cooler and better retain electrolytes. Heart
rates also stay lower, and body temperatures stay lower.

On the other end of the weather spectrum, extreme cold can make
it harder for athletes to get muscles warmed up. When chilled,
the body also tends to divert blood from the arms and legs to the
brain, heart and internal organs. In water, that can happen at
temperatures of about 10 C (50 F), Fraser said. But air
temperatures need to be much colder to cause danger.
Cross-country ski racers often successfully compete in conditions
as cold as -30 C (-22 F).

London certainly won’t be that cold, but the U.K.’s summer has
been persistently cooler and wetter than normal for the same
reason that much of the United States has been persistently hot
and dry.

As the Arctic warms twice as quickly as the lower 48 states,
there has been a weakening of the temperature gradient between
high and mid-latitude regions, said Paul Douglas, meteorologist
and founder of Weather Nation, a weather outsourcing company in
the Twin Cities, MN. As a result, the jet stream is blowing
farther north and less strongly than usual. That has caused
weather patterns of all kinds to stall.

“What we’re seeing increasingly is that the atmosphere seems to
be getting stuck in a rut,” Douglas said. “Weather systems are
just moving slower.”

In the four to five weeks leading up to the Olympics, Douglas
said, a large ridge of high pressure settled over Greenland and
Iceland, shoving storms southward and eastward to the U.K. and
Scandanavia.

The good news for athletes who prefer drier conditions is that
the U.K.’s cool, wet pattern began breaking down just before the
start of the Games. Over the next week, models predict highs in
the 60s to low-70s in London, with nighttime lows in the 50s and
no signs that flooding rains will return any time soon.

“I don’t think weather is going to be a huge factor at the
games,” Douglas said. “That may be wishful thinking.”